Fuel pump having an impeller

ABSTRACT

A fuel pump includes an impeller having a plurality of front and rear blades and a plurality of front and rear blade ditches, a pump passage around the impeller, a fuel suction port and a fuel discharge port. Each of the front and rear blade ditches has a concave surface. Each of the front blade ditches has a tip depth at the tip of the front blade and a bottom depth at a portion adjacent to the tip. The fuel discharged from the front ditches is turned by the concave surface inwardly, thereby forming circulating flow effectively.

CROSS REFERENCE TO RELATED APPLICATION

[0001] The present application is based on and claims priority from Japanese Patent Application 2001-340394, filed Nov. 6, 2001, the contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a fuel pump for pumping fuel up from a tank.

[0004] 2. Description of the Related Art

[0005] A fuel pump that has an impeller is well known, as disclosed in JP-A-9-14173. Such an impeller has a plurality of blades and blade ditches between the adjacent blades. The blade ditches are partitioned from each other by partition walls. When the impeller rotates, fuel in the blade ditches is driven radially outward under centrifugal force. The fuel in one of the blade ditches circulates along the partition walls and flows into the next one of the blade ditches. While the fuel continues to circulate, the fuel is pressurized until it is discharged from a fuel discharge port. Therefore, the pump pressure and pump efficiency can be improved if the blade ditch accepts more fuel and the fuel flows out from the ditch at a higher speed.

[0006] A fuel pump disclosed in JP-A-9-14173 has an impeller whose axial width of a blade ditch is larger than a half the axial width of the impeller, thereby preventing stagnation of the fuel in the fuel passage formed around the impeller. The blade ditch, which is formed at the intermediate portion between a blade and a partition wall, has a curved surface projecting from one axial end of the impeller toward the other axial end. The curved surface is like a parabolic surface that has a tangential line at the tip of the blade extending axially outward. Although the fuel flows from a blade ditch on one end of the impeller into one of the blade ditch on the other end, such fuel may not turn to flow to the next ditches on the opposite end of the impeller again. It is difficult to form an effective circulation flow. Because the partition wall of the impeller disclosed in JP-A-9-14173 has a zigzag surface in the circumferential direction, the impeller has blades of different sizes. Therefore, the smaller front surface of the impeller can not give fuel sufficient energy.

SUMMARY OF THE INVENTION

[0007] Therefore, the present invention has been made in view of the above problems.

[0008] An object of the invention is to provide an improved fuel pump that can increase fuel flow speed and give fuel more kinetic energy by preventing stagnation of fuel.

[0009] According to a main feature of the invention, a fuel pump includes an impeller having a plurality of front and rear blades with a plurality of front and rear blade ditches between the respective blades, a pump passage around the impeller, a fuel suction port and a fuel discharge port. Each of the front blade ditches has a front concave surface that has a first tip depth at the tip of the blade and a bottom depth that is deeper than the tip depth at a portion adjacent to the tip of the blade. Preferably, the front concave surface is a partially cylindrical surface.

[0010] Therefore, the concave surface turns fuel inward, so that a circulating fuel flow can be formed effectively.

[0011] In addition, each of the rear blade ditches has a rear concave surface that has a second tip depth at the tip of the blade and a bottom depth that is deeper than the second tip depth at a portion adjacent to the tip of the rear blade. This further increases the effect of circulating flow.

[0012] According to another feature of the invention, the first tip depth is formed to be larger than a half of a thickness of said impeller. As a result, the fuel is given kinetic energy by the blade at the front surface thereof in the rotation direction, thereby preventing stagnation of the circulating flow otherwise formed in the pump passage.

[0013] According to another feature of the invention, the front concave surface has a tangential line inclining toward the front end of said impeller at the portion that crosses the blade tip. Therefore, the shape of the circulating flow becomes approximately circular.

[0014] According to another feature of the invention, the cylindrical surface has its center inside the front blade ditch. Therefore, the fuel speed outside the blade ditches can be increased.

[0015] According to another feature of the invention, each of the front and rear blades inclines forward in the rotation direction of said impeller. Therefore, the fuel flow speed can be increased.

[0016] According to another feature of the invention, the front and rear blades are a half-pitch shifted from each other. Preferably, the second tip depth is smaller than a half the thickness of the impeller. As a result, the impeller can provides the front and rear blades without increasing the thickness.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Other objects, features and characteristics of the present invention as well as the functions of related parts of the present invention will become clear from a study of the following detailed description, the appended claims and the drawings. In the drawings:

[0018]FIG. 1 is a schematic diagram illustrating a main portion of an impeller of a fuel pump according to a preferred embodiment of the invention;

[0019]FIG. 2 is a cross-sectional side view of the fuel pump according to the preferred embodiment;

[0020]FIG. 3 is a perspective view of the impeller of the fuel pump according to the preferred embodiment;

[0021]FIG. 4 is an enlarged fragmentary perspective view of the impeller shown in FIG. 3;

[0022]FIG. 5 is an enlarged fragmentary perspective view of the impeller shown in FIG. 3;

[0023]FIG. 6 is an enlarged fragmentary side view of the impeller shown in FIGS. 1 and 3;

[0024]FIG. 7 is a schematic diagram illustrating a main portion of the impeller shown in FIG. 6 cut along line VII-VII; and

[0025]FIG. 8 is a schematic diagram illustrating a main portion of the impeller and a fuel passage.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] A fuel pump according to a preferred embodiment of the invention will be described with reference to the appended drawings.

[0027] The fuel pump 1 is usually located in a fuel tank of a vehicle as a component of an electrically controlled fuel injection system for pumping up and supplying fuel to an engine.

[0028] The fuel pump 1 includes a pump section 10 and a motor section 20. The motor section 20 is a DC motor that has a cylindrical housing 21 with a plurality of permanent magnets on the inside surface, an armature 22 that is coaxially disposed in the housing 21 opposite the permanent magnets and a brush unit. The pump section 10 includes a main casing 11, a casing cover 12 and an impeller 30. The main casing 11 and the casing cover 12 form a fuel passage member, in which the impeller 30 is rotatably supported. The impeller 30 has a front blade group 41 (left in FIG. 3) and a rear blade group 42 (right in FIG. 3). The front blade group 41 includes a plurality of front blades 32 f and a plurality front blade ditches 33 f formed between partition walls 31 and the front blade 32 f. The rear blade group 42 includes a plurality of rear blades 32 r and a plurality rear blade ditches 33 r formed between the partition walls 31 and the rear blades 32 r. The main casing 11 and the casing cover 12 are made of aluminum die-casting. The main casing 11 has a bearing 13 at the center thereof and the outer periphery force-fitted deep into an end of the housing 11. The casing cover 12 is also inserted into the same end of the housing 21 so as to cover the main casing 11 and is clamped by the edge portion of the housing 21. A thrust bearing 14 is force-fitted to a center hole of the casing cover 12 to support an end of the rotary shaft 23 in the axial direction. The rotary shaft 23 is also supported by a bearing 13 at the other end thereof.

[0029] A fuel inlet port 16 is formed at the casing cover 12, from which fuel is pumped up and supplied to a pump passage 17 when the impeller 30 rotates. The fuel supplied to the pump passage 17 is pressured while the impeller 30 is rotating and discharged to a fuel chamber 24 of the motor section 20 from a fuel discharge port (not shown) of the main casing 11. A pump groove 11 a is formed at a portion of the main casing 11 around the tips of the blades 32. Another pump groove 12 a is also formed at a portion of the casing cover 12 opposite the pump groove 11 a. The pump grooves 11 a and 12 a form a pump passage 17.

[0030] The pump groove 11 a has an end at a portion past the fuel discharge port in the rotation direction of the impeller 30. A suitable gap is formed between the circumference of the pump groove 11 a and the blade tips 32 c at the end of the pump groove 11 a past the discharge port in the rotation direction of the impeller 30. Fuel held in the blade ditches 33 f, 33 r of the impeller 30 is discharged from the pump passage 17 through the gap and the fuel discharge port.

[0031] The armature 22 of the motor section 20 has an armature core 25. A disk shaped commutator 26 is disposed at the upper end of the armature 22. Electric power is supplied via a terminal 28 of a connector 27 and the brush unit (not shown) to the commutator 26. When electric power is supplied to the armature 22, the armature 22 rotates the impeller 30. The impeller 30 pumps up fuel from the fuel inlet port 16 and supplies the fuel to the pump passage 17. Then, the fuel is given kinetic energy by the impeller and discharged to the fuel chamber 24. The fuel flowing into the fuel chamber 24 passes around the armature 22 and flows outside the fuel pump 1 from the discharge port 29.

[0032] The front blades 32 f of the front blade group 41 are ½ pitch shifted in the circumferential direction from the rear blades 32 r of the rear blade group 42. Therefore, the partition walls 31 are formed between the front blades 32 f on the front end of the impeller 30 and the rear blade ditches 33 r on the rear end of the impeller 30. As shown in FIG. 6, each of the blade ditches 33 f, 33 r is surrounded by the partition walls 31 and the blades 32. When fuel is discharged from the pump passage 17, a fuel-pressure wave caused by the front blades 32 f and a fuel-pressure wave caused by the rear blades are a half cycle shifted from each other. Therefore, noise when the fuel is discharged is reduced.

[0033] Each of the blades 32 f, 32 r inclines toward the direction of rotation of the impeller 30, as shown in FIG. 5, so that kinetic energy can be applied to the fuel held in the blades ditches 33 f, 33 r. The back side 32 a of each of the blade ditches 33 f, 33 r in the rotation direction of the impeller 30 is larger than the fore side 32 b thereof, as shown in FIG. 6. Because the fore side 32 b of the blade ditches 33 f, 33 r in the rotation direction is located just at the back of the blades 32 f, 32 r, it does not give kinetic energy to the fuel.

[0034] As shown in FIG. 1, each of the front blade ditches 33 f has the following features:

[0035] (1) A concave cylindrical surface extends from the front end 30 a of the impeller toward the rear end 30 b of the impeller 30. Each of the front blade ditches 33 f has a bottom or maximum depth a, a tip depth b at the blade tip 32 c of the blade 32. The bottom depth a of the front blade ditch 33 f is larger than tip depth b (or a>b), so that the surface of the front blade ditches 33 f are introverted at the blade tips 32 c.

[0036] (2) If the impeller 30 has an axial thickness t, the tip depth b is larger than t/2 (or b>t/2).

[0037] (3) Each of the front blade ditches 33 f has a partially cylindrical front surface C that has a tangential line L at the portion that crosses the blade tip 32 c. The tangential line L inclines to the front end 30 a, so that an angle θ formed between the tangential line L and the blade tip 32 c is smaller than 90° (or θ<90°). That is, the front concave cylindrical surface C of the front blade ditches 33 f extends toward the front end 30 a of the impeller 30. Accordingly, the fuel driven into the front blade ditches 33 f of the front blade group 41 is discharged from the blade tip 32 c toward the front end 30 a of the impeller 30.

[0038] Therefore, fuel flows into the front blade ditches 33 f from the front end 30 a of the impeller 30 is discharged to the pump passage 17 from a portion of the impeller 30 rear from the axial center thereof without stagnation, as shown in FIG. 8.

[0039] (4) The front concave cylindrical surface C of the front blade ditches 33 f has the center O located inside the blade ditch 33. Because the center O of the concave cylindrical surface C where the speed of the circulating fuel flow is the lowest, the speed of the fuel flow can be effectively increased. This effectively prevents stagnation of the fuel flow in the pump passage 17.

[0040] The rear blade ditches 33 r have substantially the same feature except for the following features, as shown in FIG. 7.

[0041] (5) Each of the rear blade ditches has tip depth b′ that is smaller than a half of the axial thickness t of the impeller 30 (that is, b′<t/2). Therefore, the front and rear blades 33 f, 33 r can be formed without increasing the axial thickness of the impeller.

[0042] (6) Each of the rear blade ditches 33 r has a rear concave cylindrical surface C′ that has a tangential line at the portion that crosses the blade tip 32 c. The tangential line inclines to the rear end 30 b of the impeller 30 in the same manner as the front concave cylindrical surface C. Accordingly, the fuel driven into the rear blade ditches 33 r of the rear blade group 42 is discharged from the blade tip 32 c toward the rear end 30 b of the impeller 30.

[0043] When the front blades 32 f of the front blade group 41 form circulating fuel flow along the front concave cylindrical surface C, the rear blades 32 r of the rear blade group 42 form another circulating fuel flow along the rear concave cylindrical surface C′. Accordingly, the front and rear blade groups 41, 42 alternately and jointly form the circulating fuel flow.

[0044] As indicated by arrows shown in FIG. 8, the fuel in the fuel passage 17 flows into the blade ditches 33 f, 33 r when the impeller 30 rotates. Because each of the front blades 32 f inclines toward the direction of rotation of the impeller 30, as shown in FIG. 5, the fuel is mainly gathered at the base portion 32 d of the front blades 32 f, so that the fuel flows along the concave cylindrical surface C and given kinetic energy by the front blades 32 f. As the fuel flows along the front concave cylindrical surface C toward the blade tip 32 c, the fuel is gradually pressed to the left or forward, so that the flow speed is increased. The fuel discharged from the front blade ditches 33 f is guided by the concave cylindrical surface C and forms circulating flow, and flows into the rear blade ditches 33 f at the base portion of the rear blade 32 r. Then the fuel flows along the rear concave cylindrical surface C′ toward the blade tip 32 c in the same manner as described above. Thus, the fuel is repeatedly pressured by the impeller 30.

[0045] All the front blades 32 f have a cross-sectional area in the rotation direction that is the same to each other, and all the rear blades 32 r also have a cross-sectional area in the rotation direction that is the same to each other. Therefore, the impeller according to the invention can form smooth circulating flow.

[0046] In the foregoing description of the present invention, the invention has been disclosed with reference to specific embodiments thereof. It will, however, be evident that various modifications and changes may be made to the specific embodiments of the present invention without departing from the scope of the invention as set forth in the appended claims. Accordingly, the description of the present invention is to be regarded in an illustrative, rather than a restrictive, sense. 

What is claimed is:
 1. A fuel pump including an impeller having a plurality of front and rear blades and a plurality of front and rear blade ditches, a passage member having a pump passage around said impeller, a fuel suction port and fuel discharge port, wherein each of said front blade ditches has a front concave surface that has a first tip depth at the tip of said blade and a bottom depth that is deeper than said first tip depth at a portion adjacent to said tip.
 2. The fuel pump as claimed in claim 1, wherein said first tip depth is larger than a half of a thickness of said impeller.
 3. The fuel pump as claimed in claim 1, wherein said front concave surface has a tangential line inclining toward the front end of said impeller at the portion that crosses said blade tip.
 4. The fuel pump as claimed in claim 1, wherein each of said rear blade ditches has a rear concave surface that has a second tip depth at the tip of said blade and a bottom depth that is deeper than said second tip depth at a portion adjacent to said tip.
 5. The fuel pump as claimed in claim 4, wherein said second tip depth is smaller than a half of the thickness of said impeller.
 6. The fuel pump as claimed in claim 1, wherein said front concave surface is a partially cylindrical surface.
 7. The fuel pump as claimed in claim 6, wherein said rear concave surface is a partially cylindrical surface.
 8. The fuel pump as claimed in claim 6, wherein said partially cylindrical surface has its center inside said front blade ditch.
 9. The fuel pump as claimed in claim 7, wherein said front and rear cylindrical surfaces respectively have centers inside said blade ditches.
 10. The fuel pump as claimed in claim 1, wherein each of said front and rear blades inclines forward in the rotation direction of said impeller.
 11. The fuel pump as claimed in claim 1, wherein said front blades are disposed at the peripheral portion of the front end of said impeller at equal pitches in the circumferential direction and said rear blades are disposed at the peripheral portion of the rear end of said impeller at equal pitches in the circumferential direction, and wherein said front and rear blades are a half-pitch shifted from each other in a circumferential direction. 